Revenue from Contracts with Customers - Revenue by Service Offering (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Revenue from Contracts with Customers
Total revenue	$ 173.7	$ 184.0	$ 524.4	$ 547.4
Subscription services
Revenue from Contracts with Customers
Revenue	160.4	170.3	485.6	506.9
Other business services
Revenue from Contracts with Customers
Revenue	5.4	5.6	16.1	16.9
Other business services - Wholesale and colocation lease revenue
Revenue from Contracts with Customers
Revenue	4.8	4.8	14.4	14.6
Other revenue
Revenue from Contracts with Customers
Other revenue	7.9	8.1	22.7	23.6
Residential Subscription | Subscription services
Revenue from Contracts with Customers
Revenue	132.7	142.6	402.4	424.6
Residential Subscription | HSD
Revenue from Contracts with Customers
Revenue	84.2	85.6	251.1	246.6
Residential Subscription | Video
Revenue from Contracts with Customers
Revenue	42.4	50.0	132.8	156.1
Residential Subscription | Telephony
Revenue from Contracts with Customers
Revenue	6.1	7.0	18.5	21.9
Business Subscription | Subscription services
Revenue from Contracts with Customers
Revenue	27.7	27.7	83.2	82.3
Business Subscription | HSD
Revenue from Contracts with Customers
Revenue	18.1	17.7	53.9	52.0
Business Subscription | Video
Revenue from Contracts with Customers
Revenue	2.9	2.8	8.8	8.4
Business Subscription | Telephony
Revenue from Contracts with Customers
Revenue	$ 6.7	$ 7.2	$ 20.5	$ 21.9